Telescopic fitment for a magnetic filter

ABSTRACT

A telescopic fitment for connection of a magnetic filter into a central heating system circuit includes a first connector and a second connector, each of the first and second connectors including a filter connection end for connecting with the magnetic filter and a circuit connection end for connecting with the central heating system circuit, at least one of the first and second connectors including an inner pipe and an outer pipe, the filter connection end being provided on one of the inner or outer pipes and the circuit connection end being provided on the other of the inner or outer pipes, the inner pipe being slideable within the outer pipe for adjusting the position of the circuit connection end with respect to the filter connection end, whilst maintaining a sealed fluid path between the circuit connection end and the filter connection end.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of priority of internationalapplication Serial No. PCT/GB2016/050187 filed on Jan. 28, 2016 herebyincorporated herein by reference in its entirety which claims thebenefit of GB1502756.8 filed on Feb. 19, 2015 and GB1521054.5 filed onNov. 30, 2015, each of which is incorporated herein by reference in itsentirety.

The present invention relates to a telescopic fitment for a magneticfilter in a central heating system, particularly for systems havingpipework with diameter between around 35 and 42 mm.

BACKGROUND TO THE INVENTION

It is now common to fit filter devices to central heating systems, toremove magnetic and non-magnetic particles from the system water as itcirculates around the system. Such filters are useful in all types ofcentral heating system, from small domestic systems with a singlecircuit and a few radiators, to the largest systems in factories andother industrial sites.

At present, filters are available for domestic systems, which typicallyuse 22 mm or 28 mm copper pipe for the main heating circuit(s). Thesefilters typically have a body made from plastics, for example,glass-reinforced nylon. Various features are known which provide foreasy and compact installation in a domestic setting. For example, theApplicant's co-pending application published as GB2502383 discloses anin-line fitment for a filter which includes two sockets, one sockethaving a greater pipe receiving depth than the other socket. Where somemanipulation of the pipework is possible, this provides for easyattachment of the fitment to the heating circuit, where the parts of thefitment which attach to the filter are guaranteed to be at exactly thecorrect spacing for attachment of the filter.

Filters are also available for larger systems, which use 2 inch (around50 mm) or greater diameter pipe for the heating circuit(s). For example,the filters sold under the trade mark “Magnaclean® Commercial” fit intothis category. These filters are essentially in the form of a large,heavy, cast container, with an inlet and an outlet on either side, aremovable lid, and magnets extending into the container to attract andretain magnetic particles from system water as it flows through thefilter. These large filters are typically connected into the heatingcircuit by providing a welded flange on the inlet and outlet of thefilter. A similar flange can be welded onto the pipe ends to beconnected, and each pipe flange is then bolted to its correspondingfilter flange, some sealing material having been placed in between.

However, there is a class of medium-sized central heating systems forwhich neither of these types of filters are particularly well suited.These systems typically use steel pipe, between 35 mm and 42 mm indiameter. The pipes are usually joined either by tapered threads, whichare typically made as required using a die, or by crimping, for exampleusing the “XPRESS®” crimping system. These pipes are inflexible, whichmakes it impossible to use the in-line fitment as described inGB2502383. Also, the size of the tools used, and the forces typicallyapplied to pipework during installation of these systems, makes damageto a plastic-bodied filter likely. However, large filters such as theMagnaclean (RTM) Commercial are expensive to manufacture, and ratherover-specified in terms of the system pressure and flow rate which istypical in medium-sized (35-42 mm) systems.

It is an object of this invention to provide a magnetic filter which issuitable for use in these medium-sized central heating systems.

STATEMENT OF INVENTION

According to a first aspect of the present invention, there is provideda telescopic fitment for connection of a magnetic filter into a centralheating system circuit,

-   -   the telescopic fitment including a first connector and a second        connector, each of the first and second connectors including a        filter connection end for connecting with the magnetic filter        and a circuit connection end for connecting with the central        heating system circuit,    -   at least one of the first and second connectors including an        inner pipe and an outer pipe, the filter connection end being        provided on one of the inner or outer pipes and the circuit        connection end being provided on the other of the inner or outer        pipes,    -   the inner pipe being slideable within the outer pipe for        adjusting the position of the circuit connection end with        respect to the filter connection end, whilst maintaining a        sealed fluid path between the circuit connection end and the        filter connection end.

The telescopic fitment is especially well-suited for use with pipeworkhaving a diameter between around 35 mm and 42 mm. This pipework istypically joined by the use of a tapered male thread which mates with astraight female thread. The circuit connection end may be provided witha straight female thread, and may be then tightened onto a taperedthread on the end of a pipe which forms part of the heating circuit. Asthe threads are tightened, the circuit connection end will move slightlyalong the tapered thread of the pipe. At some point, the connection willbe tight enough to form a seal. The other connector, which may include asimilar telescopic arrangement, may be tightened onto another pipe inexactly the same way. Because the connectors are telescopicallyadjustable, the fitment can be connected to pipework having a range ofrelative distances and positions between the two connections to theheating circuit. Also, the tapered thread connection method as describedabove may be used, without having to predict precisely how far along thetapered thread the joint will tighten and seal.

35-42 mm diameter pipes are typically made from steel, and are veryinflexible. The telescopic fitment therefore provides a similar level offlexibility in terms of positioning and alignment as is typicallyachievable in smaller (e.g. 22 mm copper) systems, where there isnormally some movability in an unconnected pipe end.

Locking means may be provided on the or each connector which includesslideable inner and outer pipes, the locking means being engageable toprevent sliding of the connector and disengageable to allow sliding ofthe connector.

Preferably, once the fitment is installed and connected to the heatingcircuit and to the filter, the locking means are engaged to preventsliding. This prevents the telescopic fitment expanding due to pressurein the heating system, when the heating system is filled and the systemwater is heated. Without the locking means, pressure in the heatingcircuit can force the telescopic fitment to expand, and in turn this canput pressure on the (preferably plastic) filter body, potentiallycausing it to crack and leak.

The locking means may be in the form of a screw thread provided on eachof the inner and outer pipes, and a screw-threaded collar for engagingwith one or both of the threads, for preventing relative movement of theinner and outer pipes when the collar is engaged with both threads, andfor allowing relative movement of the inner and outer pipes when thecollar is engaged with only one thread.

At least one of the screw threads may be provided on a rotatable butlongitudinally fixed collar on the inner or outer pipe. This allows thestart of the thread to be easily found for engaging the screw-threadedcollar, bearing in mind that the inner and outer pipes in someembodiments may be rotatable relative to one another.

The circuit connection end may be provided on the outer pipe and thefilter connection end may be provided on the inner pipe.

At least one of the outer and inner pipes may be substantially in theform of a 90 degree elbow. The filter connection end and circuitconnection end may face in substantially perpendicular directions. Itwill be understood that either pipe may be formed integrally or fromseveral connected components. Magnetic filters typically have portswhich extend parallel to each other, and yet they are usually to befitted essentially to a single straight pipe where a section has beencut out to accommodate the filter. In other words, magnetic filters areusually attached to pipe ends which are facing each other, in-line witheach other.

Nevertheless filters in some cases need to be fitted to two parallelpipes, or to pipe ends at various angles relative to each other. It istherefore envisaged that the fitment of the invention may be provided ina range of alternatives to accommodate these requirements.

An O-ring seal may be provided between the inner and outer pipes of theor each telescopic connector. Preferably, two O-ring seals are providedto ensure a leak-proof join.

The O-ring seal(s) may be provided in groove(s) on the inner pipe, andthe outer pipe may have a substantially smooth inside wall at the pointwhere it meets the seal in use.

A stop may be provided between the inner and outer pipes, to prevent theouter pipe from sliding off the inner pipe and detaching. Where anO-ring or double O-ring seal is provided, the stop may prevent the outerpipe from sliding to a point where the seal is no longer between the twopipes.

Preferably, the stop is in the form of a snap ring which is held withina groove extending around the interior of the end of the outer pipe, anda first circumferential detent on the exterior wall of the inner pipe.The snap ring, when held in its groove, forms a circumferential bulge onthe interior wall of the outer pipe, and the first detent on the innerpipe obstructs that bulge and prevents the outer pipe from moving pastthe detent.

The use of the snap ring to form part of the stop is particularlyadvantageous, because it allows for easy assembly of the telescopicfitting. A snap-ring assembly groove may be provided on the exteriorwall of the inner pipe, further inward (that is, away from the end ofthe inner pipe over which the outer pipe is slid) than the first detent.Just inward of the snap-ring assembly groove, an extension may beprovided around the external wall of the inner pipe which forms a seconddetent.

The outer pipe preferably has a tapered interior wall at the end whichis to be slid over the inner pipe, giving that end of the outer pipe amouth which is slightly wider than the diameter of the rest of the outerpipe. The groove within which the snap ring is held is preferablylocated just inward (i.e. in the direction away from the end which isslid over the inner pipe) of the tapered mouth.

To assemble the connector, firstly a metal snap ring may be placedaround the inner pipe, either over the snap-ring assembly groove or overthe inner pipe at any position between the first detent and thesnap-ring assembly groove. The outer pipe may then be slid over theinner pipe, past the seals. The tapered mouth of the outer pipe willslide over the snap ring, and the snap ring will then be carried withthe outer pipe until it reaches the snap-ring assembly groove. When thesnap ring is located over the snap-ring assembly groove, the outer pipecan continue to be pushed a short distance further onto the inner pipe.As it is, the tapered mouth will start to compress the snap-ring intothe snap-ring assembly groove, until the outer pipe has moved to thepoint where the snap-ring holding groove on the outer pipe is level withthe snap-ring assembly groove on the inner pipe. At this point, thesnap-ring will expand into the snap-ring holding groove, and the outerpipe can be extended back out, carrying the snap ring with it.

At this stage, the telescopic connector is assembled, and cannot easilybe disassembled, since there is no way of removing the snap-ring fromwithin the snap-ring holding groove. The snap-ring effectively becomes apermanent part of the outer pipe, and prevents the outer pipe frommoving past the point where the snap-ring is obstructed by the firstdetent on the inner pipe.

Note that, after assembly, the snap-ring assembly groove servesessentially no further purpose.

The filter connection end of each connector may include an arrangementwhereby part of the connector is received within an inlet/outlet port ofthe magnetic filter, and a threaded ring is provided which can betightened by hand to retain the connector in attachment with themagnetic filter. Such an arrangement is disclosed in the Applicant'sco-pending British patent application published as GB2524056, which isincorporated herein by reference.

The fitment may be provided with a magnetic filter, the magnetic filterincluding inlet and outlet ports which extend from the filtersubstantially parallel with each other. The inlet and outlet ports maybe externally screw-threaded for connection with the filter connectionends of the connectors, as described above. Preferably, the filter ismade substantially from plastics, for example glass-reinforced nylon.

Typically, the connectors of the fitment are substantially 90 degreeelbows, and when the filter connection ends are attached to the parallelinlet and outlet ports of the filter the connectors can be configured sothat their circuit connection ends face away from each other, and aredisposed along the same line. The telescopic arrangement as describedmay be provided substantially on the circuit connection ends of theconnectors, so that the distance between the circuit connection ends ofthe connectors is adjustable when they are connected to the filter asdescribed. The filter may then be installed on a straight pipe bycutting a section out of the pipe, and then adjusting the telescopingcomponents of the connectors so that the fitment is exactly the rightsize to fit the length of pipe which has been removed. The circuitconnection ends of the connectors may be internally screw threaded, inwhich case they may be connected into the circuit by cutting a taperedthread into the ends of the heating circuit pipes with a die tool, andthen screwing the circuit connection ends of the connectors onto thetapered threads. Alternatively, the circuit connection ends of theconnectors may be crimped into the central heating circuit, for exampleusing the XPRESS (RTM) crimping system.

According to a second aspect of the invention, there is provided amethod of fitting a magnetic filter to a pair of pipe ends in a centralheating system circuit,

the method making use of a telescopic fitment according to the firstaspect of the invention, the circuit connection end of each connectorbeing an internally threaded screw connection,

and the method comprising the steps of:

-   -   a) cutting a tapered thread on each of the pipe ends;    -   b) screwing the internally threaded circuit connection of each        connector onto the tapered thread of a respective pipe end;    -   c) adjusting the position of the filter connection ends of the        connectors by sliding the inner and outer pipes of the fitment        to position the filter connection ends spaced from each other at        a distance matching the distance between the inlet and outlet        ports of the magnetic filter;    -   d) attaching the filter connection end of each connector        respectively to the inlet/outlet port of the magnetic filter.

Preferably, the method further comprises the step of engaging lockingmeans to prevent sliding of the inner and outer pipes of each connectorof the fitment.

In the method, the circuit connection ends of each connector can bescrewed onto the tapered thread of the pipe end, until a watertight sealis made. One or both of the connectors can then be “telescoped” toprecisely set the filter connection ends at the correct distance apartto connect with the magnetic filter. The magnetic filter can be easilyattached. Engaging locking means protects the body of the filter, whichmay be made from plastics, from damaging forces caused by expansion ofthe telescoping parts which may be forced apart by pressure in theheating circuit.

It will be understood that any of the preferable/optional features ofthe magnetic filter and/or the telescopic fitment of the first aspect ofthe invention may be used in the way described as part of the method ofthe second aspect of the invention.

DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, and to show moreclearly how it may be carried into effect, reference will now be made byway of example only to the accompanying drawings, in which:

FIG. 1 is a perspective view of a magnetic filter provided with atelescopic fitment in accordance with the first aspect of the invention;

FIG. 2 is an exploded perspective view of the magnetic filter andfitment of FIG. 1;

FIGS. 3a and 3b are cross-sections through the magnetic filter andfitment of FIG. 1, showing the telescopic fitment in respectivelyfully-extended and fully-retracted positions;

FIG. 4 is a magnified cross-section of part of the telescopic fitment asshown in FIG. 3 a;

FIG. 5 is a perspective view of a handle member for use with themagnetic filter of FIG. 1, not forming part of the invention;

FIGS. 6a and 6b are perspective views of the filter and fitment of FIG.1, shown together with the handle member of FIG. 5 in various positions;

FIG. 7 is a cross-section through the magnetic filter and fitment ofFIG. 1, showing the direction of flow within the fitment and filter; and

FIGS. 8a, 8b, 8c and 8d are plan views from in front of a connectorforming part of another embodiment of a telescopic fitment according tothe first aspect of the invention, shown in different positions.

DESCRIPTION OF A PREFERRED EMBODIMENT

Referring firstly to FIGS. 1 and 2, a magnetic filter for a centralheating system is indicated generally at 10, and is shown with a fitment60.

The magnetic filter includes first and second substantially cylindricalseparation chambers 12, 14. Each chamber is open at one end (uppermostin FIG. 1), but the open end of each separation chamber 12, 14 is closedby a closure 16, 18. In FIG. 1 the closures 16, 18 are shown fullyfitted onto the separation chambers 12, 14. In other words, the magneticfilter 10 is shown closed, as it would be when installed in a centralheating system and in normal use.

As best seen in FIG. 2, magnets 20, 22 extend into each of theseparation chambers 12, 14. The magnets 20, 22 are fixed to the closures16, 18 and are enclosed in use by sleeves 24, 26. The arrangement of amagnet attached to a closure, and the sleeves themselves, are describedin detail in co-pending application GB1404432.5, which is incorporatedherein by reference.

An inlet port arrangement 28 and outlet port arrangement 30 areprovided, between the first and second separation chambers 12, 14. Thefirst and second separation chambers 12, 14 are disposed next to eachother and are joined to each other, and the inlet and outlet portarrangements are provided between the two separation chambers. The twoseparation chambers 12, 14, and the inlet and outlet port arrangements28, 30 are moulded from glass-reinforced nylon in a single piece.

The inlet and outlet port arrangements 28, 30 are externallyscrew-threaded.

Each closure 16, 18 is in the form of a substantially planar roofsection 40, 42, and a circumferential wall 44, 46 extending from theroof section. An external screw thread 36, 38 is provided on the outsideof each circumferential wall 44, 46, and castellations 48, 50 areprovided on the inside of the wall. The castellations 48, 50 extendsubstantially radially and inwardly from the inside of the wall, and arein the form of spaced elements around the interior of the wall. A bleedvalve 52, 54 is provided substantially in the centre of each roofsection 40, 42.

Near the top of the curved wall of each of the separation chambers 12,14, an internal screw thread 32, 24 is provided. The internal screwthreads 32, 34 correspond with external screw threads 36, 38 on theclosure members 16, 18. Hence the closure members 16, 18 can be screwedinto the top of the separation chambers 12, 14, to form a plug and sealthe open end of the separation chambers.

A drain outlet is provided in the base of each separation chamber, and adrain plug 56 substantially in the form of a bolt is provided to closeeach drain outlet when the filter 10 is in use.

The fitment 60 comprises a first connector 62 and a second connector 64.In this embodiment the connectors 62, 64 are identical to each other,and are substantially in the form of 90 degree elbows. Each connectorhas a filter connection end 66 and a circuit connection end 68. Thecircuit connection ends 68 of each connector 62, 64 in use are connectedinto a central heating system circuit, and the filter connection ends 66are connected to the magnetic filter 10, in particular to the inlet portarrangement 28 and the outlet port arrangement 30. As shown in FIG. 1,in use system water flows into the filter via the uppermost connector 62(arrow A) and flows out of the filter via the lowermost connector 64(arrow B).

Referring now to FIGS. 3a, 3b , and 4, the fitment 60 will be describedin more detail.

The filter connection end 66 of each connector 62, 64 is substantiallyidentical to those disclosed in co-pending application published asGB2524056, and is not described in detail here. Briefly, the filterconnection end includes a fitment adapted to be received within at leastone of the ports of the separator, the fitment including a bore forcarrying fluid from/to the central heating circuit to/from theseparator, and a threaded connector for securing the fitment to the oreach port, the threaded connector having a grip area for facilitatingtightening of the connector by hand.

The circuit connection end 68 is telescopic, and so can be extended (asshown in FIG. 3a ) and retracted (as shown in FIG. 3b ) whilstmaintaining a sealed flow path between the circuit connection end 68 andthe filter connection end 66. The telescopic components are shownfully-extended in FIG. 3a , and fully retracted in FIG. 3b , but it willbe appreciated that the fitment 60 can also work with the telescopiccomponents in any intermediate position. Also, the telescopic parts ofeach connector 62, 64 could be equally extended, or have differingextents.

The telescopic circuit connection end 68 broadly includes an inner pipe70 and an outer pipe 72. The outer pipe slides over the inner pipe toincrease or decrease the total length of the circuit connection end 68.As seen best in FIG. 4, two O-ring seals 74, 76 are provided in groovesnear the end of the inner pipe 70. The double seal ensures that fluiddoes not leak from the connector. The outer pipe has a tapered mouth 78,and a groove 80 just inward of the tapered mouth 78 which holds asnap-ring 82. The snap-ring 82 travels with the outer pipe 72 as it ismoved (upwards and downwards in FIG. 4) with respect to the inner pipe70. A first detent 84, in the form of a ring around the outside wall ofthe inner pipe, stops the mouth 78 of the outer pipe sliding over theO-ring seals 74, 76. The snap-ring 82 which is carried with the outerpipe 72 is obstructed by the first detent 84 when the telescopic partsare at maximum extension, preventing the parts coming apart orcompromising the seal.

A second detent 86 is provided on the outside of the inner pipe 70,spaced some distance into the inner pipe 70 (i.e. towards the filterconnection end). Adjacent to the second detent 86 and between the firstand second detents 84, 86 is a snap-ring assembly groove 88. Thesnap-ring assembly groove is used when assembling the connector 64—thesnap ring 82 can be placed around the inner pipe 70, between the firstdetent 84 and the assembly groove 88. The outer pipe 72 can then bepushed onto the inner pipe 70. As this is done, the snap-ring willtravel in the mouth 78 of the outer pipe 72 until it reaches theassembly groove 88 and is obstructed from further travel along the pipe(upwards in FIG. 4) by the second detent 86. At this point, as the outerpipe 72 is pushed slightly further over the inner pipe, the increasinglynarrow interior of the outer pipe 72 will compress the snap ring 82 intothe groove 88, until the holding groove 80 of the outer pipe 72 is levelwith the snap ring 82. At this point, the snap ring 82 will snap intothe holding groove 80, and the outer pipe 72 becomes permanently fixedto the inner pipe 70.

The outer pipe 72 is the part which is joined into the heating circuit.This may be via a screw connection in which case an interior thread maybe cut into the end of the outer pipe 72, or it may be via a crimpingsystem, or by any other means. In the case where a screw connection isused, the outer pipe may be rotated with respect to the inner pipe, thetwo pipes being rotatable as well as slidable in the telescopingarrangement. Alternatively, a separate screw-threaded rotatable part maybe provided in some embodiments.

Referring now to FIGS. 5, 6 a and 6 b, a handle member is indicatedgenerally at 90. Note that although several handle members 90 are shownin FIGS. 6a and 6b , this is merely to show the handle 90 in differentpositions. It is envisaged that only one handle member 90 will beprovided with each filter 10, since the handle 90 is a multipurposetool.

The handle member 90 is substantially elongate, having upper, lower,left and right side faces 92, 94, 96, 98 and two opposing end faces 100,102. The lower face 94, the right side face 98 and one of the end faces102 are hidden in FIG. 5 but all faces are shown in at least one of thepositions in FIGS. 6a and 6b . In any case, the left and right sidefaces 96, 98 are identical, as are the two opposing end faces 100, 102.

On each opposing end face 100, 102, a rectangular cut-out or indent 104is provided. The cut out extends all the way to the edge of the end face102, 104 which meets the lower face 94, but stops short of each of theother three edges of the end face 102, 104. The rectangular cut-out 104on each end of the handle 90 is designed to engage with the radialcastellations 48, 50 which are provided on the interior of thecircumferential wall 44, 46 of each of the closures 16, 18. When thehandle 90 is engaged, it sits at least partly below the top of the walland castellations of the closure 16, 18, between opposing sides of thewall 44, 46. FIG. 6a shows the handle in position to be engaged with theclosure 16 in this way, indicated by arrow C.

A hexagonal male protrusion 111 is provided on the upper surface 92 ofthe handle 90, and is preferably sized at 22 mm across flats. Thehexagonal male protrusion 111 can be engaged with a socket wrench orspanner which can then be used to apply torque to the handle, ifrequired.

When the handle is positioned between opposing sides of thecircumferential wall 44 of closure 16, it may be turned clockwise oranticlockwise to tighten or loosen the closure 16, as required. This canbe done by hand or by using a socket wrench or spanner as describedabove. Indeed, using any other tool is difficult. This is an advantage,because where closures can be gripped by large spanners or the like,over-tightening is a risk and can lead to damage to the plasticseparation chamber, and to the seal of the closure on the separationchamber. The handle generally allows tightening and loosening of theclosure 16 by hand, but over time the closure may become tighter andmore difficult to loosen by hand. In that case, a socket wrench orspanner may be used. However, the arrangement of the handle assemblyprovides a practical limitation as to the types of tools which may beused, therefore reducing the risk of damage caused by over-torquing.

On each side face 96, 98 of the handle member 90, a square socket 106 isprovided within a substantially square extension 108. The square socketis sized to operate bleed valve 52, and also other bleed valves whichare typically found on most radiators and other central heating systemcomponents. The handle 90 is seen in the correct position to operate thebleed valve 52 in FIG. 6a , indicated by arrow D.

Two identical hexagonal sockets 110 are provided in the lower face 94 ofthe handle 90. These are best seen in FIG. 6a on the handle 90 indicatedby arrow E. The sockets are disposed at either side of a circular indent112 which is substantially in the centre of the lower face 94.

The hexagonal sockets 110 allow the handle to be used as a spanner tooperate the bolt 56 which forms the drain plug on the separator chamber14, as shown in FIG. 6b , indicated by arrow F.

Referring now to FIG. 7, the construction of the inlet arrangement 28will be described in more detail. The flow path within the outletarrangement is substantially Y-shaped, the flow from the inlet connector62 through the inlet port being split into two, part of the flow beingdirected into each of the first and second separation chambers 12, 14.The inlet arrangement 28 is fluidly connected with each separationchamber 12, 14 through an aperture in the curved wall of the cylindricalseparation chamber, and the flow enters the separation chambersubstantially parallel to the curved wall, at the point where the curvedwall meets the inlet arrangement 28. In other words, flow enters eachseparation chamber at a tangent. As a result, a swirl of flow is createdin each of the two chambers 12, 14, as indicated by arrows G.

The outlet arrangement 30 is not seen in the cross-section of FIG. 7,but it is substantially identical and, in fact, either port can be usedas the inlet, with the other port being used as the outlet. Note thatthe flow deflector 114 which defines the centre of the Y-shaped flowpath in each inlet/outlet arrangement 28, 30 has a curved profile in theplane defined by a circular section of the cylinder—i.e. the plane inwhich the cross section of FIG. 7 is shown. This reduces pressure dropwhich would otherwise be caused at the outlet when the flow has to turna sharp corner into the substantially tangential outlet arrangement 30.It is found that, with this size of filter, this arrangement givesacceptable results in terms of pressure drop.

Referring now to FIGS. 8a to 8d , a connector forming part of a secondembodiment of a fitment according to the invention is indicatedgenerally at 62′. The connector 62′ is in most material respects similarto the connector 62 and the common parts will not be described again indetail. The connector 62′ includes a filter connection end 66′ and acircuit connection end 68′, the circuit connection end 68′ beingtelescopic having an inner pipe 70′ and an outer pipe 72′.

The second embodiment of the fitment includes two identical connectors,as shown and described.

The connector 62′ further includes a collar 120, which is internallyscrew threaded. The outer pipe 72′ is provided with a matching externalscrew thread, and the collar 120 is provided screwed onto the outer pipe72′, as shown in FIG. 8a . An external screw thread 122 is also providedon the inner pipe 70′, via an externally screw threaded collar 124 whichis rotatable on the inner pipe 70′, but at a fixed longitudinalposition.

The collar 120 can be engaged to lock the telescopic connector in anextended position, a retracted position, or in any intermediateposition. When the telescopic inner and outer pipes are slid to theirdesired relative position, the screw threaded collar may be rotated tomove it longitudinally along the pipe until it engages with the screwthread 122 on the externally threaded collar 124. Because the externallythreaded collar 124 is rotatable, the start of the thread can be foundwithout rotating the inner and outer pipes relative to each other. Whenthe collar 120 is engaged with both threads, relative sliding of theinner and outer pipes 70′, 72′ in either direction is prevented.

FIG. 8a shows the connector 62′ with the telescoping arrangement fullyretracted and the holding means disengaged; FIG. 8b shows the connector62′ with the telescoping arrangement fully extended and the holdingmeans disengaged; FIG. 8c shows the connector 62′ with the telescopingarrangement fully retracted and the holding means engaged; and FIG. 8dshows the connector 62′ with the telescoping arrangement fully extendedand the holding means engaged. It will be understood that the holdingmeans can be also engaged when the telescoping arrangement is in anyintermediate position between the fully-extended and fully-retractedpositions.

The filter and fitment provides for a high-performance and economicalfilter which is useful in systems where a typical domestic filter wouldbe too small, and where a known commercial filter would beover-specified and unnecessarily expensive. The filter can be made fromplastics, in particular glass-reinforced nylon or glass-reinforcedpolypropylene, but safeguards are provided against damage caused bypressure on the filter body from the steel pipes. The fitmentarrangement allows easy fitting to inflexible pipework.

The embodiments described above are provided by way of example only, andvarious changes and modifications will be apparent to persons skilled inthe art without departing from the scope of the present invention asdefined by the appended claims.

We claim:
 1. A telescopic fitment for connection of a magnetic filterinto a central heating system circuit, the telescopic fitment includinga first connector and a second connector, the first connector and thesecond connector each including a filter connection end for connectingwith the magnetic filter and each including a circuit connection end forconnecting with the central heating system circuit, at least one of thefirst connector and the second connector including an inner pipe and anouter pipe, the filter connection end being provided on one of the inneror outer pipes and the circuit connection end being provided on theother of the inner or outer pipes, the inner pipe being slideable withinthe outer pipe for adjusting the position of the circuit connection endwith respect to the filter connection end, whilst maintaining a sealedfluid path between the circuit connection end and the filter connectionend, in which locking means are provided, the locking means beingengageable to prevent sliding of the inner pipe with respect to theouter pipe following sliding of those pipes to an extended position, aretracted position, or any intermediate position, in which the lockingmeans includes a first thread provided in a fixed longitudinal positionon the outer pipe, a second thread provided in a fixed longitudinalposition on the inner pipe, and a threaded collar for engaging with oneor both of the first and second threads on the outer and inner pipes, inwhich at least one of the first thread and the second thread is providedon a rotatable, but longitudinally fixed collar on the respective one ofthe outer pipe and the inner pipe.
 2. A telescopic fitment as claimed inclaim 1, in which the circuit connection end of each of the first andsecond connectors is provided with a straight female thread.
 3. Atelescopic fitment as claimed in claim 1, in which the filter connectionend of each of the first and second connectors is provided by the innerpipe and the circuit connection end of each of the first and secondconnectors is provided by the outer pipe.
 4. A telescopic fitment asclaimed in claim 1, in which at least one of the outer pipe and theinner pipe is substantially in the form of a 90 degree elbow, the filterconnection end and the circuit connection end of the connector facing insubstantially perpendicular directions.
 5. A telescopic fitment asclaimed in claim 1, in which one or both of a first O-ring seal and asecond O-ring seal is provided between the inner pipe and the outer pipeof each telescopic connector.
 6. A telescopic fitment as claimed inclaim 5, in which one or both of the first and second O-ring seals areprovided in one or more grooves on the inner pipe, and in which theouter pipe has a substantially smooth inside wall which slides adjacentone or both of the first and second O-ring seals in use.
 7. A telescopicfitment as claimed in claim 1, in which a stop is provided between theinner pipe and the outer pipe, to prevent the outer and inner pipes frombecoming detached from each other.
 8. A telescopic fitment as claimed inclaim 7, in which the stop is in the form of a snap ring held within aholding groove near the end of the outer pipe, and a first detent on theexterior wall of the inner pipe.
 9. A telescopic fitment as claimed inclaim 8, in which a snap-ring assembly groove is provided on theexterior wall of the inner pipe, inward of the first detent.
 10. Atelescopic fitment as claimed in claim 9, in which an extension forminga second detent is provided around the external wall of the inner pipe,inward of the snap-ring assembly groove.
 11. A telescopic fitment asclaimed in claim 8, in which the outer pipe has a tapered mouth at oneend.
 12. A telescopic fitment as claimed in claim 11, in which theholding groove on the outer pipe is located inward of the tapered mouth.13. A telescopic fitment as claimed in claim 1, in combination with amagnetic filter, the magnetic filter including inlet and outlet portswhich extend from the filter substantially parallel with each other. 14.A telescopic fitment and a magnetic filter as claimed in claim 13, inwhich the magnetic filter includes a filter body made substantially fromplastics or glass-reinforced nylon.
 15. A telescopic fitment and amagnetic filter as claimed in claim 13, in which the inlet and outletports are externally screw-threaded for connection with the filterconnection ends of the first connector and the second connector.
 16. Atelescopic fitment as claimed in claim 1, in which the threaded collaris provided on one of the outer pipe and the inner pipe, in engagementwith the respective one of the first thread and the second thread,wherein the threaded collar is rotatable to longitudinally move thethreaded collar along the outer pipe or the inner pipe such that itmoves into or out of engagement with the other of the first thread andthe second thread.
 17. A method of fitting a magnetic filter to a pairof pipe ends in a central heating system circuit, the method making useof a telescopic fitment according to claim 1, the circuit connection endof each of the first connector and the second connector being aninternally threaded screw connection, and the method comprising thesteps of: a) cutting a tapered thread in each of the pipe ends; b)screwing the internally threaded circuit connection of each of the firstconnector and the second connector onto the tapered thread of arespective pipe end; c) adjusting the position of the filter connectionends of the first connector and the second connector by sliding theinner pipe and the outer pipe of the fitment to position the filterconnection ends spaced from each other at a distance matching thedistance between the inlet port and the outlet port of the magneticfilter; d) attaching the filter connection end of the first connectorand the second connector respectively to the inlet/outlet port of themagnetic filter.
 18. A method according to claim 17, further comprisinga step of engaging the locking means to prevent sliding of the inner andouter pipes of each connector of the fitment relative to each other.